For inspection of scratches or dirt on tire, automatic visual inspection equipment of tire is generally known, which automatically inspect visual appearance of tire through shooting an image of tire surface by setting up an imaging device such as a CCD camera, for example, in an inspection line.
In this automatic visual inspection equipment, since the inspection (or measurement) is performed while a tire to be inspected is rotated, an upper rim and a lower rim are fixed to the tire and the tire in that condition is connected to a main shaft which is coupled with a motor and the like.
In conventional automatic visual inspection equipment of tire, the upper rim is fixed to the tire from upper side thereof, the tire being placed substantially in horizontal way, hence the weight of the upper rim causes deformation of tire when rim-assembly is carried out in this manner for a tire with low rigidity. Deformation of tire generates a misalignment of the upper rim with respect to the main shaft. If the main shaft is rotated in this state, the tire rotates with eccentricity (the amount of eccentricity is not less than 0.3 mm) and such a situation occurs as the image object goes out of a visual field, which causes difficulty of image analysis which follows thereafter.
Although FIGS. 7 to 9 are not described in patent documents, there is shown a process of tire rim-assembling according to a rim-assembling mechanism in the aforementioned conventional automatic visual inspection equipment of tire.
The conventional rim-assembling mechanism includes a lower rim 300 which is fixed to the lower surface of tire T, an elevating device (not shown) of the lower rim 300, an upper rim 200, and a main shaft 100 which is rotatable and coupled to a motor, for example, that is not shown in the drawing.
At the lower end of the main shaft body 100, an upper rim fixing portion 120 is provided via a smaller diameter portion 110. On the top surface of the upper rim 200, a corresponding protruding conical surface 220 is formed, which engages with a concave conical surface that is formed on an upper rim fixing portion 120 of the main shaft 100 via a connecting portion 210 with small diameter.
In other words, when the upper rim 200 and the main shaft 100 are connected, connection and positioning are performed in combination of mating tapered surfaces with each other of the main shaft 100 and the above mentioned conical surface 220 of the upper rim 200.
In the above-mentioned conventional automatic inspection equipment of tire, when the upper and lower rim is fixed onto the tire T, firstly, as shown in FIG. 7, in a state that the tire T is fixed on the lower rim 300, the lower rim 300 is elevated up by an elevating mechanism (not shown).
Subsequently, as shown in FIG. 8, the upper surface of the tire T is connected to the upper rim 200. After connection of the upper rim 200, the rim-assembled tire T is elevated up further in a state that the tire T is subjected to the load of the upper rim 200, so as to engage and integrate the conical surface 220 at the upper end of the connecting portion 210 formed integrally with the upper rim 200 and the concave conical surface formed in the upper rim fixing portion 120 at the lower end of the main shaft 100.
Next, after the tire T is rim-assembled and connected to the main shaft (in a condition where the tire T is inflated and press-contacted onto the main shaft), the main shaft 100 is rotated, for example, with a motor as shown in FIG. 9 so that the rim-assembled tire T which is fixed thereto is rotated, and necessary inspection is carried out by shooting it with a fixed camera.
In conventional automatic visual inspection equipment of tire, the upper rim 200 is fixed from above onto the tire T which is placed horizontally as described above, and thereby weight of the upper rim 200 is directly applied on the tire T. Hence, the tire T is deformed if the rigidity of the tire T is small compared with the tire weight. When the tire T is deformed, the upper rim 200 placed on the tire T also causes displacement, hence when it is fixed to the main shaft 100, a delicate displacement is generated between the main shaft 100 and the axis of tire. When the tire T is rotated in that condition, the tire T is eccentrically-rotated.
When the amount of eccentricity reaches, for example, more or less 0.3 mm, shooting of the tire T with a camera provided at a fixed position may cause such a problem as a predetermined shooting object goes out of the visual field of the camera.